Deep Brain Stimulation (DBS) has been used to treat ailments such as Parkinson's disease, depression, epilepsy, paralysis, obsessive-compulsive disorder, essential tremor, dystonia, chronic pain, sleep disorder etc. In DBS, a neurosurgeon uses an implantable lead deep into the brain and inject currents into target neuron sites via its electrodes. These sites include Subthalamic Nucleus (STN), the Globus Pallidus Internal (GPi) etc. The target sites are very small (e.g., STN is ˜4 mm diameter, 9 mm long ovoid). Accurately locating the target site and implanting a lead close to its center are critical to stimulate only the targeted neurons.
To locate the target site, currently a neurosurgeon inserts a recording micro-electrode that senses electrical signals produced by neurons. If the sensed signal is not identical to a desirable pattern, he retracts it and inserts another recording micro-electrode along a different trajectory. He repeats the process several times until he identifies a target site that will offer the best possible results. But the multiple passes of inserting/retracting recording electrodes in and out of the brain several times can rupture the fine blood vessels in the brain. Further, these multiple passes can take several hours. Reduction of this surgical time will obviously require micro-electrodes embedded within a DBS lead.
Implanting a lead exactly at the center of a target site right at the first time is currently nearly impossible as MRI, stereotactic equipment and brain shifts limit the accuracy. But currents from such off-centered lead can unintentional stimulation of neurons outside the target site, causing serious side effects such as suicidal tendency, double vision, worsened speech, dizziness etc. Reduction of such side effects will obviously require a large number of macro-electrodes, so a select group of macro-electrodes can be steered or focused only on the target neurons.
Prior art leads and systems are open loop, meaning that they do not contain recording micro-electrodes that are necessary for closed loop control. Examples of such prior art open loop leads include, a 4-electrode lead (model 3389) by Medtronic Inc., MN as described in U.S. Pat. No. 8,805,541, an 8-electrode lead by Boston Scientific, MA as described in U.S. Pat. No. 8,792,993, a 12-electrode lead by Aleva Neurotherapeutics SA, Switzerland as described in M. Hariz, “Deep Brain Stimulation: New Techniques”, in Parkinsonism and Related Disorders, 2014, p. 192-196. This publication also describes a 32-electrode lead by Sapiens Steering Brain Stimulation, Netherlands. The Sapiens lead employs pad type electrodes that can entangle in the brain if they fail. This lead also does not contain micro-electrodes. A recent closed loop system by Medtronic Inc., MN, termed Activa® PC+S, uses two leads with four macro-electrodes at two different target sites. This system also does not contain micro-electrodes. Such prior-art open loop leads require substantially long surgical time; they are also prone to serious side affects as it is difficult to implant the lead close to the center of the target site right at the first instance.